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891.
Samaneh Keshani Mohammad Hossein Montazeri Wan Ramli Wan Daud M. Mohsen Nourouzi 《Drying Technology》2013,31(7):784-795
Wall deposition is one of the most conventional problems in the spray drying process. The operation of a spray dryer is affected by the wall deposition fluxes inside the equipment. In this study, computational fluid dynamic (CFD) simulation was used to investigate the effect of spray dryer geometry on wall deposition. A CFD model was developed for different geometries of spray dryer with a conical (case A) or a parabolic (cases B and C) bottom. The results implied that the parabolic geometry resulted in a lower deposition rate on the spray dryer walls. A comparison of results using the P-values (F-test) of the air velocity, in the conical and parabolic geometries, showed that there was a significant difference in air stability between them. The flow field in conical geometry case A was significantly more unstable, and parabolic geometry case C produced the most uniform airflow patterns. Moreover, the higher wall shear stress in case C, with lower values of the vorticity, would result in less wall deposition. 相似文献
892.
Fatemeh Hosseinzadeh Hossein Sarpoolaki Hassan Hashemi 《International Journal of Applied Ceramic Technology》2014,11(4):681-698
This article develops a new intuitionistic fuzzy multi‐attribute group decision‐making model to solve precursor selection problems. The proposed model is based on a hybridization of intuitionistic fuzzy sets theory, grey relational analysis and technique for order performance by similarity to ideal solution method. To better describe the uncertain decision environment, multi‐attribute group decision‐making method with completely unknown weights of both experts and attributes is proposed in an intuitionistic fuzzy setting. Finally, the selection of the carbon source in synthesis of nanocrystalline titanium carbide powders by sol‐gel route as an application example is solved by the proposed model, and the implementation of the model is illustrated completely. 相似文献
893.
Muzammil Ali Tariq Mahmud Peter John Heggs Mojtaba Ghadiri Dusan Djurdjevic Hossein Ahmadian Luis Martin de Juan Carlos Amador Andrew Bayly 《Chemical Engineering Research and Design》2014
A one-dimensional numerical model for a detergent slurry drying process in a counter-current spray drying tower is developed for the prediction of the gas and droplet/particle temperature profiles within the tower. The model accommodates droplets/particles over a range of sizes. A semi-empirical slurry droplet drying model is integrated with a counter-current tower simulation based on mass, energy and particulate phase momentum balances in order to calculate the drying rate and the particle residence time within the tower. The coupled first order ordinary differential equations for the two phases are solved numerically using the iterative shooting method in an algorithm developed within MATLAB. The predictions of the numerical model are compared with industrial pilot plant data. The results are found to vary significantly with the specified size distribution of the droplets. Despite the simplicity of the model in ignoring the coalescence, agglomeration, wall deposition and re-entrainment, the model gives reasonable agreement with the experimental data. 相似文献
894.
Mojtaba Movahedi Amir-Hossein Kokabi Hamid-Reza Madaah-Hosseini Mahdi Kiani 《Metals and Materials International》2011,17(4):665-670
In the present study, the roll bonding behaviour of Al-3003/Al-4043 and Al-3003/Zn sheets were compared. The bi-layer sheets
were produced by a roll bonding process at different reductions in thickness and rolling temperatures. The joint strengths
of the sheets were evaluated by peel and bend testing before and after supplemental annealing treatment. The peeled surfaces
were examined using a scanning electron microscope. The results indicated that the Al-3003/Al-4043 sheets were bonded with
higher joint strength and lower threshold reductions in thickness with respect to the Al-3003/Zn sheets. In contrast to the
Al-3003/Zn sheets, significant improvement was observed in the joint strength of the Al-3003/Al-4043 sheets after annealing
treatment. Moreover, electron microscopy examinations showed that the fracture types of the Al-3003/Al-4043 and Al-3003/Zn
sheets were predominantly ductile and brittle, respectively. 相似文献
895.
Hossein Ghalkhani Saeed Golian Bahram Saghafian Ashkan Farokhnia Asaad Shamseldin 《Water and Environment Journal》2013,27(4):535-548
Developing a robust flood forecasting and warning system (FFWS) is essential in flood‐prone areas. Hydrodynamic models, which are a major part of such systems, usually suffer from computational instabilities and long runtime problems, which are particularly important in real‐time applications. In this study, two artificial intelligence models, namely artificial neural network (ANN) and adaptive neuro‐fuzzy inference system (ANFIS), were used for flood routing in an FFWS in Madarsoo river basin, Iran. For this purpose, different rainfall patterns were transformed to run‐off hydrographs using the Hydrologic Engineering Center (HEC)‐1 hydrological model and routed along the river using HEC river analysis system RAS hydrodynamic model. Then, the simulated hydrographs with different lag times were used as inputs for training of ANN and ANFIS models to simulate flood hydrograph at the basin outlet. Results showed that the simulations obtained from ANN and ANFIS coincided with the results simulated by the HEC‐RAS, and application of such models is strongly suggested as a backup tool for flood routing in FFWSs. 相似文献
896.
Molecular dynamic simulation of carbon dioxide,methane, and nitrogen adsorption on Faujasite zeolite
Removing impurities such as carbon dioxide and nitrogen from natural gas is a technical challenge and one of the major concerns in natural gas treatment process. In this study, adsorption of CH4, N2, and CO2 on the Faujasite(FAU) zeolite has been studied using molecular dynamics simulation at temperatures of 293, 308, and 323 K and pressures up to 1 MPa. COMPASS force field was used to model the interactions between zeolite and guest molecules. Ewald and atom-bas... 相似文献
897.
A new class of aromatic poly(urea-imide)s having biphenylene pendant group was prepared by the diphenyl azidophosphate (DPAP) activated one-pot polyaddition reaction of a preformed imide ring-containing dicarboxylic acid, 4-p-biphenyl-2,6-bis(4-trimellitimidophenyl)pyridine ( 1 ) with various aromatic diamines. A model compound was also synthesized by the reaction of diimide-dicarboxylic acid 1 with two mole equivalents of aniline. In this direct method the polymers were prepared by polyaddition reactions of the in situ-formed diisocyanate with the aromatic diamines. The inherent viscosities of the polymers were measured in the range of 0.11–0.15 dL g−1. The ultraviolet λmax values of the poly(urea-imide)s were also determined. Furthermore, crystallinity of the resultant polymers was evaluated by wide-angle X-ray diffraction method, and they exhibited nearly a noncrystalline nature. All of the resulting polymers exhibited excellent solubility in common polar solvents. The glass transition temperatures of the polymers determined by DSC thermograms were in the range 241–272°C. The temperatures at 10% weight loss from their TGA curves were found to be in the range 406–437°C in nitrogen. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
898.
An analytical guidance law of planetary landing mission by minimizing the control effort expenditure
Hamed Hossein Afshari Alireza Basohbat Novinzadeh Jafar Roshanian 《Journal of Mechanical Science and Technology》2009,23(12):3239-3244
An optimal trajectory design of a module for the planetary landing problem is achieved by minimizing the control effort expenditure.
Using the calculus of variations theorem, the control variable is expressed as a function of costate variables, and the problem
is converted into a two-point boundary-value problem. To solve this problem, the performance measure is approximated by employing
a trigonometric series and subsequently, the optimal control and state trajectories are determined. To validate the accuracy
of the proposed solution, a numerical method of the steepest descent is utilized. The main objective of this paper is to present
a novel analytic guidance law of the planetary landing mission by optimizing the control effort expenditure. Finally, an example
of a lunar landing mission is demonstrated to examine the results of this solution in practical situations. 相似文献
899.
4‐(4′‐Aminophenyl)urazole (AmPU) was prepared from 4‐nitrobenzoic acid in six steps. The reaction of monomer AmPU with n‐isopropylisocyanate was performed in N,N‐dimethylacetamide solutions at different ratios, and the resulting disubstituted and trisubstituted urea derivatives were obtained in high yields and were finally used as models for polymerization reactions. The step‐growth polymerization reactions of AmPU with hexamethylene diisocyanate, isophorone diisocyanate, and toluene‐2,4‐diisocyanate were performed in N‐methylpyrrolidone solutions in the presence of pyridine as a catalyst. The resulting novel polyureas had inherent viscosities of 0.11–0.18 dL/g in dimethylformamide at 25°C. These polyureas were characterized with IR, 1H‐NMR, elemental analysis, and thermogravimetric analysis. Some physical properties and structural characterization of these novel polyureas are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2692–2700, 2003 相似文献
900.
Evaluating the geometric characteristics of cylindrical features 总被引:1,自引:0,他引:1
This paper presents mathematical models and efficient methodologies for the evaluation of geometric characteristics that define form and function of cylindrical features; namely cylindricity and straightness of median line. These two problems have similar structures and can be solved by comparable procedures. Based on the proposed methodologies, the cylindricity error evaluation can be performed using any of the following criteria: the least squares cylinders, minimum circumscribed cylinders, maximum inscribed cylinders or minimum zone cylinders. The procedures have been tested for accuracy and efficiency. The results indicate that they provide accurate results quickly. 相似文献